1. Field of the Invention:
This invention relates to a water-proof mount mechanism for a camera of the lens-interchangeable type.
2. Description of the Related Art:
There have been two kinds of water-proof mount mechanisms adapted for lens-interchangeable type cameras.
The water-proof mount mechanism of the first kind has been arranged to have an annular elastic member disposed on an abutting face for abutment in the direction of the optical axis of the camera, as disclosed for example, in Japanese Utility Model Publication No. SHO 61-39403.
The water-proof mount mechanism of the second kind has been arranged as shown in FIG. 4 of the accompanying drawings. Referring to FIG. 4, the illustration includes a camera-side mount 1; a protruding part 1b; an abutting face 1c of the camera-side mount 1; a leaf spring 2; a mirror box 3; a camera exterior member 4; a mirror 5; a focusing screen 6; a pentagonal prism 7; a lens-side mount 10; a claw 10a of the lens-side mount 10; an abutting face 10b of the lens-side mount 10; a lens exterior member 11; a groove 11b; a lens glass carrying frame 12; lens glasses 13 and 14; and a ring-shaped elastic member P4. In other words, a water-proof mount mechanism is arranged as follows: The protruding part 1b which is disposed at the peripheral end of the camera-side mount 1 protrudes toward the lens. The lens exterior member 11 is provided with the groove 11b. The ring-shaped elastic member P4 is arranged in the groove 11b to be in pressure contact with the inner circumferential face of the protruding part 1b when the lens is mounted on the camera body.
In the conventional mechanism of the first kind mentioned in the foregoing, the elastic member is disposed at the abutting face for abutment in the direction of the optical axis. This mechanism does not ensure that a predetermined distance required between the camera body and the lens in the direction of the optical axis is kept unvarying, because the distance is dependent upon the pressure of the elastic member. The required precision for the distance between the camera body and the lens in the direction of the optical axis is very severe. In order to solve this problem, the force of an urging member for abutment in the direction of the optical axis must be increased. However, the increase in the force of the urging member increases a torque required for mounting and dismounting the lens and thus degrades the operability of the camera system in mounting and dismounting the lens.
Meanwhile, in the case of the conventional mechanism of the second kind, the elastic member is arranged to come into contact in a direction perpendicular to the optical axis. This arrangement relieves the mechanism from the above-stated problem of the mechanism of the first kind. However, in cases where the camera system must be arranged to permit use of a lens which is interchangeable in respect of a mount dimension but is not provided with any water-proof arrangement, as shown in FIG. 5, the mechanism of the second kind presents the following problem: The outside diameter of the above-stated protruding part lb inevitably increases because the inside diameter of the protruding part 1b must be arranged to escape from a lens exterior member 11' of a lens having a maximum diameter. Even in a case where the camera system is designed only for water-proof lenses, the outside diameter of the protruding part 1b can hardly be reduced as this part must be arranged to permit use of any of them that has the largest diameter among them. Besides, the camera system in this instance does not have interchangeability with a lens of the ordinary kind having an outside diameter larger than the inside diameter of the protruding part 1b.
Further, Japanese Laid-Open Utility Model Application No. SHO 57-82324 discloses an arrangement which is similar to the structural arrangement of FIG. 4. In the case of that application, although a groove and a ring-shaped elastic member are provided on the side of the camera body, the groove is formed along the inner side of a tubular part. Therefore, it is normally impossible to mount an ordinary interchangeable lens.